Grinding blocks



Sept. 12, 1961 R. SCHUSTER GRINDING BLOCKS 2 Sheets-Sheet 1 Filed May 9, 1957 INVENTOR. ROMA/v -Fem 0375a fim/V/ Z I I United States Patent {and 2,999,742 GRINDING BLOCKS Roman Schuster, Funk Weg 14, Seuden (lller), Germany Filed May 9, 1957, Ser. No. 670,354 Claims priority, application Germany May 11, 1956 6 Claims. (Cl. 51-293) The present invention relates to grinding blocks for use in grinding strips of wood or like ledges.

A grinding machine for grinding wood strips is known in which an endless rotating emery belt is urged, by means of a block adapted to the section strip, against the section strip which is fed at a uniform rate through the machine. This machine will grind only rounded strips but not strips having contours with sharp corners and edges, since the grinding belts cannot be conformed to the sharp edges and corners. Thus workpieces of wood, more particularly strips having contours with sharp edges and corners must be hand ground.

It is an object of the invention to provide means achieving a novel method of mechanically grinding or treating wood workpieces having contours of any kind, more particularly workpieces having sharp edges and corners.

According to the invention, a grinding block is made of a material shaped to the contour of a ledger strip to be ground by means of the strip itself, whereafter the distances between the contour corners and edges of the grinding block are calculated in the development of the contour and finally an emery strip is formed with parallel recesses or perforations spaced apart by the aforesaid distances.

It is another important object of the invention to provide means facilitating the application of an abrasive. or emery sheet to an effective contour with sharp edges and corners of a grinding block without causing breakage of said sheet.

Other objects and advantages 'of the invention will ensue from the description of an embodiment of the invention and with reference to the accompanying drawings, in which,

FIG. 1 is a cross-section through a mould for casting a grinding block by means of a sheet material covered strip;

FIG. 2 is a bottom view of the grinding block seen somewhat in perspective and as depicted in FIG. 1, but drawn on a reduced scale;

FIG. 3 illustrates the block shown in FIG. 1 with adhesive strips for calculating the development of the contour;

FIG. 3a is a side elevation of a grinding block made of resilient material;

FIG. 4 is a plan view, to a reduced scale, of the adhesive strips shown in FIG. 3;

FIG. 5 is a plan view of apparatus for perforating emery strips; 7

FIG. 6 is a longitudinal sectional view through the apparatus shown in FIG. 5, and 7 FIG. 7 is a cross-section taken along the line VIIVII of FIG. 6.

According to the invention, the grinding block is advantageously produced as a casting of the section strip or ledge to be ground, it being possible to use for this block a casting of hardening plastic, such as synthetic resin, alabaster plaster or the like.

Referring to FIG. 1, a piece 2 of the ledge or strip to be ground is introduced into a casting mould 1. The contour forming sharp corners and edges of said ledge or strip have the references 3-6, 7 and 8 respectively. Before being introduced into the mould, the strip 2 is covered with a pattern or blank sheet 9 of paper or like sheet material of a thickness s rssp ng ns to the thick- "ice ness of an emery sheet which is to be subsequently stretched over the block 11. When the sheet 9 is stuck on, care must be taken to ensure that it is exactly conformed to and follows all the corners and edges 3 to 8.

Advantageously, a metal rod 12 of iron or the like is cast into the grinding tool block 11 and serves to strengthen the same. The rod 12 prevents subsequent deformation of the cast block 11. To improve the anchorage, the rod 12 can be formed with recesses 13. The rod 12 is also formed with tapped bores 14 so that the block 11 can be secured to a reciprocating carriage 16 by screw threaded pins 15 (FIG. 3).

The rigid plastic block illustrated in FIGS. 1 to 3 is well adapted to grind raw (cut) wood section strips but is less satisfactory for grinding wood strips covered with chalk. Since chalk covering is not of uniform thickness, the surface of the strips is uneven and considerable time would be required if a rigid section grinding block were to be used to grind such strips smooth. To ensure that the grinding block is well adapted to such chalk-covered strips, the grinding block is produced from resilient synthetic substances such as rubber, cork or the like. This grinding block is first produced with a contour substantially corresponding to the edges and corners forming the contour of said strip 2 and then the face of the grinding block taking up said contour is finish-ground through the agency of the strip 2 and an emery sheet stretched over the same. To improve still further the adaptation of such a resilient grinding block to the uneven or contoured surface of the strip, a resilient grinding block 17 can, as shown in FIG. 3a, be formed with a number of transfer slots 8.

After the grinding block has been produced in the manner hereinbefore described, the distances between the edges and corners 3 to 8 in the development of the contour are calculated as shown in FIG. 3, a thin adhesive pattern or blank sheet .19 being stuck transversely to the grinding block 11 so as to bear accurately against the contour, whereafter the corners and edges 3' to 8 bear markings on or are marked on the sheet 19 in pencil or the like and the sheet 19 is then removed and stretched. The stretched sheet in its developed form is shown in FIG. 4, the markings bearing the references 3a to 8a. The distances between the markings have the references b to f. According to the invention, parallel recesses or perforations separated by the distances b to f are now correspondingly contrived in or imparted to the paper or cloth side of an emery sheet 10 (of emery paper or emery cloth). To this end, the emery sheet can be scratched but advantageously the device illustrated in FIGS. 5 to 7 is used to contrive parallel perforations 20 in the emery sheet. Preferably, to this end, toothed discs 21 having relatively small teeth 22 contrive relatively small spaced apart apertures or perforations in the emery sheet 10, as shown in FIG. 5. The discs 21 correspond to the copying wheels used to produce paper patterns in tailoring. The resultant perforations 20 enable the emery sheet to be bent sharply about the block 11 and may follow its contour without any risk of breaking, so that the perforated emery sheet 10 is exactly conformed to the sharp corners and edges 3 to 8. This exact adaptation of the emery sheet makes it possible to grind or work upon strips having sharp corners and edges satisfactorily.

The device illustrated in FIGS. 5 to 7 is provided with a rotatable spindle 24 on which the discs 21 can move and be located. The discs 21 are spaced apart by appropriate tubular spacer members 25 and rigidly secured to the spindle 24 by means of a locknut 26. The toothed roller 21, 24, 25 co-operates with a matching roller 27 which can be rotated by means of a hand crank 23 and has a covering 28 of resilient material, such as 3 rubber. The spindle 24 is rotatably mounted in rocking levers 29 fitted to a spindle 30. An arm 31 secured thereto has an adjusting screw 32 for regulating the pressure at which the two rollers 24, 25, 21 and 27 are urged against one another.

The frame 33 of the device also has a transverse spindle 34 on which 'a guide plate 35 can be moved transversely and located by means of a nut 36. The guide plate 35 has a stop ledge 37 which, as shown in FIG. 5, is in bearing relationship with the emery sheet and guides the same.

Various changes and modifications may be made without departing from the spirit and scope of the present invention and it is intended that such obvious changes and modifications be embraced by the annexed claims.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. The method of producing a grinding tool; comprising the steps of applying a pattern sheet to a strip having corners and edges so that said sheet conforming to the contour of said strip and overlies same, casting a block on said strip supported contoured pattern sheet to conform the corresponding face of the block to said contour, providing markings on said pattern sheet at the locations of said corners and edges of the contour of said block thus formed, removing said pattern sheet, imparting to an emery sheet perforations corresponding to said markings on said pattern sheet so that said perforations run parallel to and spaced from each other through said emery sheet, and then connecting said emery sheet to said block face whereby said perforations coincide with said corners and edges, thereby to conform said perforated emery sheet to said block face so that said perforated emery sheet may be bent sharply without causing breakage thereof at said corners and edges.

2. A grinding tool comprising a block support having a substantially straight contour on one face thereof provided with sharp corners and edges, said contour being complementary to a work piece to be ground and an emery sheet provided with parallel perforations corresponding to and coinciding with said corners and edges, said emery sheet being retained on said block face thereby to conform said emery sheet to said corners and edges at said perforation without causing breakage of said emery sheet thereat and to constitute sharp cutting corners and edges on said tool.

3. The method of producing a tool for grinding wood and like workpieces; comprising the steps of applying a paper sheet to a strip having relatively sharp corners and edges with said sheet casting to the contour of said strip, forming a block of material onto said contoured sheet to conform to the corresponding face of the block to said contour, providing markings on said paper sheet at the locations of said corners and edges of the contour of said block thus formed, removing said paper sheet, copying said markings from said paper sheet onto an emery sheet, perforating said emery sheet corresponding to said markings on said paper sheet, and then anchoring said emery sheet on said block face whereby the perforations of said emery sheet coincide with said corners and edges, so that said perforated emery sheet may be bent sharply without causing breakage thereof at said corners 4 and edges and constitutes sharp cuttingcor'ners and edges for grinding purposes.

4. The method of producing a tool for treating wood and like workpieces; comprising the steps of placing into mold means a strip having relatively sharp corners and edges forming the contour of said strip, casting a block on the exposed contour of said'strip in said mold means, so as to conform totlie corresponding face of the block to said contour of said strip, placing an emery sheet onto said block face, marking said corners and edges on said emery sheet, imparting to said emery sheet parallel and spaced apart perforations corresponding to said markings, and then anchoring said-emery sheet on saidblock face whereby said perforationscoincide with said corners and edges, so that said emery sheet is conformed to said block face and said perforated emery-sheet is bent sharply without causing "breakage thereof at said corners and edges. 7

5. The method of producing a tool for grinding .profiled wooden workpieces having corners and edges forming the contour and face of said workpiece;-comprising the steps of applying to a strip a pattern sheet capable of conforming to the corners and edges of the contour and face of said strip, casting a block onto said pattern sheet thus conformed, whereby the face of the block adjacent said pattern sheet corresponds to said contour of said strip, indenting said pattern sheet at the locations of said corners and edges of the contour of said block thus formed, copying on an emery sheet the indentations from said pattern sheet in developed form position, subjecting said emery sheet accordingly to perforating action so that perforations are obtained in said emery sheet in spaced and parallel relation to each other, and then securing said emery sheet over said contoured face of said block, whereby said perforations coincide with said corners and edges and facilitate adaptation to said corners and edges of said block face, while said emery sheet may be bent sharply thereon Without causing damage to said emery sheet.

6. The method of producing a grinding block covered with an emery sheet, which serves to grind strips-of wood or the like; comprising the steps of shaping the grinding block to the contourof the strip to be ground, marking the distances between corners and edges of the contour of the grinding block, transferring the marked corners and edges onto an emery sheet, and finally forming in said emery sheet parallel perforations spaced apart from each other corresponding to the aforesaid distances for application to said block.

References Cited in the file of this patent UNITED STATES PATENTS 151,847 Cochran June 9, 1874 494,471 Gardner 1 Mar. 28, 1893 626,300 Rogers et a1 June 6, 1899 1,522,056 Hanson Jan. 6, 1925 1,922,248 Kelly .--2 Aug. 15,1933 1,931,979 Chandler Oct. 24, 1933 2,018,366 Klause r Oct. 22, 1935 2,423,293 Ciell July 1, 1947 2,467,596 Pratt Apr. 19, 1949 

1. THE METHOD OF PRODUCING A GRINDING TOOL, COMPRISING THE STEPS OF APPLYING A PATTERN SHEET TO A STRIP HAVING CORNERS AND EDGES SO THAT SAID SHEET CONFORMING TO THE CONTOUR OF SAID STRIP AND OVERLIES SAME, CASTING A BLOCK ON SAID STRIP SUPPORTED CONTOURED PATTERN SHEET TO CONFORM THE CORRESPONDING FACE OF THE BLOCK TO SAID CONTOUR, PROVIDING MARKINGS ON SAID PATTERN SHEET AT THE LOCATIONS OF SAID CORNERS AND EDGES OF THE CONTOUR OF SAID BLOCK THUS FORMED, REMOVING SAID PATTERN SHEET, IMPARTING TO AN EMERY SHEET PERFORATIONS CORRESPONDING TO SAID MARKINGS ON SAID PATTERN SHEET SO THAT SAID PERFORATIONS RUN PARALLEL TO AND SPACED FROM EACH OTHER THROUGH SAID EMERY SHEET, AND THEN CONNECTING SAID EMERY SHEET TO SAID BLOCK FACE WHEREBY SAID PERFORATIONS COINCIDE WITH SAID CORNERS AND EDGES, THEREBY TO CONFORM SAID PERFORATED EMERY SHEET TO SAID BLOCK FACE SO THAT SAID PERFORATED EMERY SHEET MAY BE BENT SHARPLY WITHOUT CAUSING BREAKAGE THEREOF AT SAID CORNERS AND EDGES. 